The present invention relates to a sales data processing apparatus and, more particularly, to an improvement in a sales data processing apparatus which can perform inventory control.
Conventionally, a sales data processing apparatus which can check the stock level of a certain item on hand or in a warehouse (i.e., can perform inventory control) is known. Such a sales data processing apparatus is described in Japanese Patent Disclosure No. 56-110175. This apparatus comprises a memory for storing the stock level of every type of item or of every section of items. Every time a certain item is registered, i.e., sold, the number of items registered is subtracted from the stock stored in the memory. Thus, the current stock can be calculated and then, the stock level printed in a summary report.
However, in the conventional inventory control method, satisfactory inventory control cannot be performed. For example, assume that a certain item is in an out-of-stock state (i.e., the stock thereof is zero) when the stock of the item is printed on a summary report. In this case, a retainer cannot know how long (or how many days) the out-of-stock state has continued. For this reason, he cannot judge to what extent sales are influenced by the out-of-stock state of the item.